1. Field of the Invention
The present invention relates to a receiving layer transfer material, more specifically to the receiving layer transfer material capable of forming an image provided with both a visual effect due to a relief forming layer and an image represented by colorant, as well as an image forming method and an image-formed object using such a transfer material.
Particularly, the present invention relates to the receiving layer transfer material provided with a special decorative image and/or stereoscopic image having a relief structure such as hologram or diffraction grating, as well as a thermal transfer image, on the object, using a thermal transfer recording system. The present invention further relates to the image forming method and the image-formed object using such a transfer material.
Furthermore, the present invention relates to the receiving layer transfer material and transfer sheet capable of obtaining a highly designable image provided with a thermal transfer image and white diffusion light or white reflection light into a specific angle range from the relief forming layer, by printing and forming the thermal transfer image by a thermal transfer printing system, onto a dye receiving layer on the relief forming layer having a white reflection function. The present invention further relates to the image forming method and the image-formed object using such a transfer material or sheet.
2. Description of the Related Art
Conventionally, a transfer foil having a relief structure such as hologram or diffraction grating can represent a special decorative image or stereoscopic image. And, the hologram or diffraction grating requires a sophisticated technology for producing the same and difficult to produce. Thereby, the hologram or diffraction grating is used for a security purpose such as forgery prevention. For example, they are used in cards such as credit card, ID card or prepaid card. They are also used in cash vouchers such as gift voucher, check, bill, stock (share) certificate or entrance ticket, since they cannot be reproduced on a color copier. Also, they have a use to be transferred onto various ID photos of driver's license, passport or the like. Furthermore, because of their specific designability, they are often used in wrapping paper, book, pamphlet, POP and so on.
In order to apply such a relief structure as hologram or diffraction grating onto an object, a transfer method using a transfer foil is known. The transfer foil is provided with a release layer, a relief forming layer having a pattern such as hologram or diffraction grating, a reflection layer, and an adhesive layer, which are sequentially stacked (layered) on a substrate. In order to transfer and print the transfer foil, a hot stamping or thermal transfer with hot roll is typically known. In the thermal transfer, a transfer foil is disposed between a heated metal stamp or roll and an object, and the transfer foil is compressed onto the object by the stamp or roll, and then the substrate is removed.
Recently, a technology for combining the relief forming layer such as hologram or diffraction grating and printed image (thermal transfer image) by a thermal transfer printer is required, in order to improve designability and the security purpose.
Therefore, in the receiving layer transfer material and the transfer sheet, there is a need for a full-colored feature, a good visibility regardless of an observation point, a good color reproducibility even in the case of observation at an observation point within a wide range, a natural image without losing color balance, an easiness to be produced, and an easiness of transferring a thermal transfer image onto the relief forming layer. On the other hand, in the image forming method and image-formed object using such a receiving layer transfer material and the transfer sheet, it is required to obtain a highly designable full color image.
Conventionally, a technology is disclosed in which a hologram transfer layer is disposed on a printed image (e.g. Japanese Patent Application Laid-open No. H6-83258). However, the hologram is attached on the printed image only to protect the image. It is not possible to dispose a printed image on the hologram.
Another technology is disclosed in which a hologram transfer foil is provided with a dye receiving layer, so that a printed image is formed onto the dye receiving layer by a thermal transfer printed and then transferred onto the object (e.g. Japanese Patent Application Laid-open Nos. H6-83259, H7-186515, H7-314925, H8-39945, H11-42863 and 2001-191653). However, since the printed image with dye is formed before the hologram transfer, there is a defect that the printed image cannot be formed after the hologram transfer. Furthermore, after the transfer layer including the hologram is transferred onto the object, the release layer is exposed on the surface of the transfer layer. Therefore, it is difficult to form the thermal transfer image on the transfer layer, since it is difficult to transfer and fix the colorant and thereby difficult to form the printed image, especially in the case of printing with a thermal transfer printer using a sublimation type thermal transfer sheet having a dye layer containing a sublimation dye.
These transfer foils may be of transparent reflection type. However, if it has an opaque type metallic reflection layer, the underlying image cannot be viewed at a part where the hologram is transferred.
Furthermore, a technology is disclosed in which a hologram transfer layer is provided with a colorant layer therein, so that a metallic color hologram is transferred onto an object (e.g. Japanese Patent Application Laid-open No. 2000-218908). However, there is a defect that the transferred color is limited to a color of the colorant layer, and thereby an image cannot be represented with various colors.
Furthermore, there is disclosed a highly designable image obtained by forming an image of dots each having a fine area onto an object by a thermal head, with a use of a thermal transfer sheet using three kinds of OVD (Optical Variable Device) each having a spatial frequency for rendering an observed color will be one of three primary colors RGB, in a specific observation point, as an image display medium for viewing a true full color image without any chromatic aberration, provided with OVD such as hologram or diffraction grating (e.g. Japanese Patent Application Laid-open No. H11-5373). However, since a full color image is reproduced only at a specific observation point, the color balance is lost and the reproduced color is deteriorated, even with slightly deviation of the observation point. Particularly, a human face seems extremely pale or red from another observation point, which gives a very unnatural impression. Thus, the greatest defect of the conventional technologies is in a fact that a direction of an observer is limited to one direction in order to view a full color image, and a true color is not reproduced when observed from any other directions.
Furthermore, the second defect is a fact that black cannot be reproduced properly, unless the underlying color of print is black, which gives a limitation of the underlying color. In order to represent black in the conventional art, a case that a diffraction light of OVD is zero, i.e. a case that dots each having fine area are not printed by the thermal head, is defined as “black”, whereas white color is represented by equalizing a total amount of fine dots among each three colors RGB.
Therefore, if the underlying color of the object is white when printing, for example if a person wearing black hairs is printed in a conventional art, the black hair portion is not printed. Thereby, white color of the underlying color is viewed, which gives an unnatural impression as if the person wears white hairs. Thus, in the conventional art, the color of the object where an image is formed has a limitation, and a true full color image cannot be displayed.